Devise: sign in with two possible encrypted passwords

My app works with the Devise gem for authentication, but I want customize it for sign in with two possible encrypted passwords, due to my previous app worked with MD5. I've two fields in my users table: encrypted_password and encrypted_old_password (I've created), I want check if exists the value encrypted_password and if the password sent matches the one set, otherwise, check if it does with MD5 and if true, then replace the value encrypted_password.

How I do this?

I don't know if my answer is fancy, but works for me. I hope someone can improve what I did.

class SessionsController < Devise::SessionsController

  def create
    recover_old_password unless user_signed_in?

    resource = warden.authenticate! auth_options
    set_flash_message(:notice, :signed_in) if is_navigational_format?
    sign_in resource_name, resource

    respond_with resource, :location => after_sign_in_path_for(resource)
  end

  def recover_old_password

    email = params[:user]['email']
    pass  = Digest::MD5.hexdigest params[:user]['password']

    @user = User.find_by_email_and_encrypted_old_password(email, pass)

    if @user.blank?

      resource = warden.authenticate! auth_options
      respond_with resource, :location => after_sign_in_path_for(resource)

    elsif

      if !@user.encrypted_password.nil?
        @user.encrypted_password = BCrypt::Password.create params[:user]['password']
        @user.save
        create
      end  

    end

  end

end